Siddle right in line behind it and that could be the end of Archer's spell. The Sussex man has sent down 28 overs of express pace and taken 2-59. The new ball due in an over, big decisions for captain Root.

Andy: The Aussies can’t complain about the short stuff, Cummins deliberately targeted Archer so he’s just giving as good as he got, and what happened to smith could have happened to Archer. People in glass houses...

Rebecca: I don’t want to see anyone injured or concussed but when Pat Cummins bowled at Chris Woakes like that it was ok? When Archer does it to Smith everyone is up in arms.

Nipped back off the seam at 92.7mph, followed by a bouncer at 91.9mph. Testing stuff for Siddle. Even the knuckle ball is timed at 90mph.

Michael Vaughan
Ex-England captain on BBC Test Match Special

There are not many players on debut who clear the bars like Jofra Archer has.

A.S: That ball didn't even hit him on the helmet, the fact that he got up from that shows what a fighter Steve Smith is.

Ben Stone: Absolutely relentless and brutal bowling from Jofra. Right decision for Smith to come off, as much as he didn’t want to leave the field. Very glad he is OK. Epic, testing period of Test match cricket.

The floodlights on again at Lord's as the clouds come over again. Nine overs 0-11 for Leach and it will be Archer again.

Luke Gray: Not comfortable with people booing Smith off. At the end of the day it’s a game of cricket, someone being hit in the head by a 90+ mph ball irrespective of what’s he done isn’t something you want to see ever.

This is the first injury Smith suffered this afternoon, when the ball thudded into his forearm. Just to reiterate, another ball from Archer felled him shortly afterwards and Australia's key batsman has retired hurt on 80.

A very strange atmosphere around the ground now as Peter Siddle comes to the crease. Archer with this short straight run of his and still able to reach 95mph. Straight through Cummins at 92mph with the final ball of the over and the crowd back on their feet.

Mitchell Johnson
Ex-Australia bowler on BBC Test Match Special

We have always said it is part of the game. The team was right behind Archer and we saw Cummins doing it the other day but it makes you feel sick in the gut.

I feel for the doctor that has to make that decision as well.

They are showing the replay and it is disturbing, the ball seems to catch him on the side of the neck.

Smith is being told he has to come off. He doesn't look very happy about it but he is going to retire hurt on 80. The crowd give him a standing ovation. Remarkable scenes at the Home of Cricket. Few could have expected this.

Stephan Shemilt
BBC Sport at Lord's

In an instant, the mood around Lord's has turned. Before Smith was struck, the crowd was baying, will Archer to bring the thunder. When he went down, there was immediate concern for the man booed to the crease. Silence as he was treated, encouraging applause as he got back to his feet.

Mitchell Johnson
Ex-Australia bowler on BBC Test Match Special

Smith looks like he feels like he's OK but he didn't look OK when he was flat on his back.

Smith is on his feet and the physios are talking with him. Concern all round. They are not showing a replay of that delivery.

Postpublished at 14:36 British Summer Time 17 August 2019

14:36 BST 17 August 2019

Oh my goodness. This was horrible and Smith has been felled by a short ball from Archer. There is a stunned silence around the ground.

Mitchell Johnson
Ex-Australia bowler on BBC Test Match Special

That wasn't a confident shot.

Pull shot - in control this time and Smith helps it away backward of square for his 11th four.

The end of Leach's eighth over - 0-10 for the left-arm spinner - and the crowd can now be treated to the next installment of Archer against Smith.